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Work, Energy, and Power — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysicsWork, Energy, and Power3 Marks
Question
A ball is given a speed v on a rough horizontal surface. The ball travels through a distance l on the surface and stops.
  1. What are the initial and final kinetic energies of the ball?
  2. What is the work done by the kinetic friction?
✓

Answer

  1. Initial kinetic energy of the ball, $\text{K}_\text{i}=\frac{1}{2}\text{mv}^2$
Here, m is the mass of the ball.
The final kinetic of the ball is zero.
Work done by the kinetic friction is equal to the change in kinetic energy of the ball.
  1. $\therefore$ Work done by the kinetic friction $=\text{K}_\text{f}-\text{K}_\text{i}$
$=0-\frac{1}{2}\text{mv}^2$
$=-\frac{1}{2}\text{mv}^2$

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